Magnetic mine detonator system

ABSTRACT

A marine minesweeping system is disclosed as incorporating a permanently magnetized steel pipe, having a polyurethane foam type buoyancy controller disposed in the bore thereof, with one end of said pipe effectively connected to a helicopter by means of a suitable length cable for the towing thereof thereby. A chain tail-like stabilizer is effectively connected to the other end of said pipe to improve the attitude stability thereof, as it is towed through water, sea water, or the like, in sufficient proximity with magnetic responsive marine mines to effect the detonation thereof.

Untied States atent [191 [11] 3,826,215 Dyjak July 30, 1974 [54] MAGNETIC MINE DETONATOR SYSTEM 3,159,806 12/1964 Piasecki 114/23; B X

l k i l4 [75] Inventor g DyJak Panama 3,383,3 1 i/l gg 11 1/22 1 1; ii

[73] Assignee: The United States of America as Primary Examiner-Lloyd L. King represented by the Secretary of the Assistant ExaminerRandolph A. Reese Navy, Washington, DC. Attorney, Agent, or Firm-Richard S. Sciascia; Don D. 22] Filed: Sept. 7, 1973 Dtyi Harvey Dav'd [21] Appl. No.: 395,331 [57] ABSTRACT A marine minesweeping system is disclosed as incor- [52] 18.81. 114/221 R, 102/ porating a permanently magnetized steel pipe, having lit. 2 R a polyurethane foam yp y y controller [58] Flew Search g 221 5 posed in the bore thereof, with one end of said pipe 114/235 35/ 0 effectively connected to a helicopter by means of a suitable length cable for the towing thereof thereby. A [56] References C'ted chain tail-like stabilizer is effectively connected to the UNITED STATES PATENTS other end of said pipe to improve the attitude stability 2,353,360 7/1944 Ronning 114/235 8 X thereof, as it is towed through water, sea water, or the 2,397.209 3/1946 Schaelchlin 114/221 R like, in sufficient proximity with magnetic responsive 2,762,009 9/l956 Sontheimer 335/302 X marine mines to effect the detonation thereofi 3,034,471 5/1962 Aschinger 114/235 B 3,121,889 2/1964 Gentile 9/9 21 Claims, 4 Drawing Figures II l TRACTOR VEHICLE (HELICOPTER) I2 PERMIi/VENT MAG/Ell. FJ ;3 if emu/v STAB/L/Z'fi MAGNE TIC :94/\/ L8 ==&O\=O; 0 4; AMCM PIPE OPTIONAL 21 I j)\ FLOAT MAGNETIC MINE DETONATOR SYSTEM STATEMENT OF GOVERNMENTINTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for Governmental purposes without the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION The present invention relates, in general, to magnetic field producing systems and, in particular, is a magnetic minesweeping system. In even greater particularity, the invention is a system for expeditiously detonating, neutralizing, or sweeping magnetic marine mines that have been deployed in an aqueous medium, such as at various and sundry water depths, and especially in shallow water depths, of the kind that are found in harbors, estuaries, bays, rivers, lakes, and the like.

DESCRIPTION OF THE PRIOR ART Heretofore, numerous magnetic field producing systems have been employed to sweep magnetic marine mines, some of which have been satisfactory for some specific purpose, but most of which have left a great deal to be desired. For example, electrical generators have driven electromagnets to, in turn, effect electromagnetic fields which are then towed along the surface of the water or dragged along the seafloor in such manner that the magnetic field generated thereby caused any magnetic responsive marine mines in proximity therewith to be detonated. However, such devices were exceedingly cumbersome and, as a general rule, did not produce the best possible magnetic field for minesweeping purposes.

In addition, such devices as railroad rails have been permanently magnetized and dragged along the sea floor or suspended between floats located at the water's surface. Unfortunately, such devices were cumbersome, too; as a matter of fact, they were so much so that it was practically impossible to sweep mines deployed in shallow water in any reasonable period of time. Hence, using such apparatus was dangerous to military or other personnel attempting to sweep marine mines in harbors, estuaries, bays, rivers, and the like, if while so doing they were also exposed to enemy attack for an excessively long period of time.

SUMMARY OF THE INVENTION The subject invention overcomes most of the disadvantages of the known prior art, in that it is quite effecnew and improved permanent magnet assembly.

tive as a marine mine sweeper and, comparatively speaking, is considerably easier to handle, and operate. Such improvements are, of course, due to the simplicity of the system and the components thereof, as well as the relative ease of construction and operation thereof. For instance, basically speaking, the invention is composed of any appropriate tractor vehicle which tows a unique but simply constructed permanently magnetized pipe assembly incorporating polyurethane flotation means and front and rear attachment means. To the rear end thereof is attached a tail which, in effect, constitutes a stabilizing means therefor, when under tow.

It is, therefore, an object of this invention to provide an improved marine minesweeping system.

A further object of this invention is to provide an improved method and means of effecting a predetermined permanent magnetic field at a given specific location or along an elongated area within any predetermined environmental medium.

Another object of this invention is to provide an improved method and means for generating a plurality of tandemly disposed magnetic fields.

Another object of this invention is to provide an improved permanet magnet that may be towed at a speed of the order of seventeen knots in water.

Another objectof this invention is to provide a permanent magnet that has a dampened and, thus, reduced natural resonant frequency, thereby also having a reduced mechanical Q.

Another object of this invention is to provide a pipe permanent magnet having a minimum of six gauss of magnetic field intensity one foot from each end thereof.

Another object of this invention is to provide a permanent magnet that may be streamlined and finstabilized, if so desired.

Another object of this invention is to provide a magnetic marine minesweeping system that is less vulnerable to mine explosions per se and which is more safely operated by human beings during military operations.

Another object of this invention is to provide a permanently magnetized mine countermeasure magnet that is relatively easy and economical to manufacture, maintain, store, and use.

Other objects and many of the attendant advantages will be readily appreciated as the subject invention becomes better understood by reference to the following detailed description, when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a quasi-pictorial elevational view showing the operation of the subject invention as a marine minesweeping system;

FIG. 2 is an elevational view of the airborne mine countermeasure (AMCM) pipe of FIG. 1;

FIG. 3 is a cross-sectional view of the pipe of FIG. 2 taken at section A-A thereof; and

FIG. 4 is a generalized, diagrammatical, pictorial representation of a magnetic responsive apparatus countermeasure system incorporating a plurality of tandemly disposed AMCM pipes towed by boat, submarine vehicle, space craft, aircraft, landcraft, or other vehicle, within any given environmental medium for any appropriate purpose.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. I, the minesweeping system constituting this invention is shown as including a tractor vehicle 11, which is preferably a helicopter, but may be any other type aircraft, water surface craft, subsurface craft, or land craft, as desired, for any given operational circumstance. However, in this particular instance, since a marine minesweeping situation is illustrated as being the operational circumstance, the preferred embodiment tractor vehicle 11 is considered to be a helicopter that is towing by means of a cable or line 12 a permanently magnetized mine countermeasure pipe (AMCM) l3 assembly within water, sea water, or the like 14, for the purpose of effecting the detonation or sweeping magnetically responsive marine mines 15 and 16 laying on or buried in the sea floor 17, respectively.

"Another cable or line 18 tows a chain or other stabilizer 19 behind AMCM pipe assembly 13, in order to provide attitude stabilizing drag at the rear end thereof, as it is being towed through said water. If desired, said stabilizer 19 may be provided with float 20 or other buoyancy control means having any desired buoyancy characteristics; however, it should be understood that so doing is optional, since it ordinarily is unnecessary. Magnetic flux 21 emanates from pipe assembly 13 essentially as shown.

The aforesaid AMCM pipe assembly 13 is depicted in somewhat more specific detail in FIGS. 2 and 3. As shown therein, it contains a magnetized hollow-steel iron, or other ferrous material pipe 22, the material of which should be selected to retain its permanent magnetism in an optimum manner, with the possible shock conditions to which it is most likely to be exposed taken into consideration.

Although numerous materials would be suitable for the making of said pipe 22, it has been found that steel appears to be the best material for such purpose; hence, it will be employed herein as the preferred embodiment. Disposed within the hollow bore of pipe 22 is a polyurethane or polystyrene foam 23 (NH COC, H and C H CHzCH respectively) having many pockets of captive air or other gaseous bubbles. The density of said polyurethane foam should be such as will make mine countermeasure pipe assembly 13 have whatever buoyancy is desired in order to make it float naturally at whatever water depth is desired. It, of course, would be well within the purview of the artisan having the benefit of the teachings presented herewith to make such polyurethane selection, both as to material density and quantity, for any given operational circumstances.

A pair of tow eyes 24 and 25 respectively attached to the opposite ends of pipe 22 facilitate the towing thereof individually or in a tandem series, as desired.

Pipe 22 is permanently magnetized by any suitable method and means. For example, a coil energized by direct current electricity (not shown) may be slipped over the length thereof, thereby causing it to become magnetically polarized with a north magnetic pole at one end thereof and a south magnetic pole at the other end thereof. Obviously, so doing is so easy that it may be done at the factory or in the field. Moreover, the permanent magnetism therof may be renewed quite readily in the field between uses, in the event the original magnetism thereof was somewhat reduced by shock waves from detonating mines or other types of impacts, merely by carrying the energizing coil and power generator therewith as adjuncts thereto, say, in the tractor vehicle or some other vehicle or station operatively associated therewith.

FIG. 4, in addition to depicting a series of AMCM pipe assemblies 13 being towed in tandem, also discloses and/or suggests that any system configuration thereof may be towed by a boat, submarine vehicle, spacecraft, aircraft, landcraft, or any other suitable vehicle 26 through any predetermined environmental medium 27 such as, for instance, water, air, space, or nal s manL y lL s P252929, stbq nfls: encing, detonating, neutralizing, or sweeping of any magnetically responsive mines land, marine, or other or any other magnetically responsive devices. Furthermore, at the tail end of the system of FIG. 4 is shown a streamline version 28 of the magnetic AMCM pipe assembly. Included therein is a rounded nose pipe body 29 and stabilizer fins 30. Of course, any other appropriate geometrical configuration may be used therefor, if so desired, if so doing would facilitate the moving thereof in a predetermined manner through some predetermined ambient environment medium.

MODE OF OPERATION The operation will now be discussed briefly in conjunction with FIG. 1 of the drawing.

The operation of the invention, like the aforementioned structure thereof, is exceedingly simple. As permanently magnetized pipe assembly 13 is moved into proximity with mines 15 and 16 by towing, pushing, or suitable self-propulsion means magnetic flux 21 emanates therefrom and travels through water 14 and sea floor 17 (or other medium or mediums ambient thereto, such as, for example, the atmosphere) and triggers the magnetic response mechanisms of said mines 15 and 16, thereby effecting the detonation thereof.

As a general rule, the polyurethane foam 23 disposed in pipe 22 is designed to make the pipe-foam assembly 13 float on or near the surface of the water in which the mines to be swept are thought to be deployed, and for most of such operational situations such design is quite satisfactory. However, in some situations it may be necessary to design the polyurethane foam portion of the pipe-foam assembly to have such buoyancy characteristic as to make pipe assembly 13 float at some predetermined water depth (rather than on or near the surface thereof), in order to tow or otherwise move it into such position as to put it in optimum magnetically influencing proximity therewith. Hence, so doing should be considered as falling within the scope of the invention.

It should, of course, be understood that the primary purpose of the subject invention is to effect the detonation of magnetic responsive marine mines; nevertheless, it should also be understood that the unique magnetic pipe assembly that is, pipe assembly 13, which, in essence, is the heart of the minesweeping system may be used in combination with the remainder of the system, if necessary, to actuate, trigger, or otherwise magnetically affect or influence any other magnetically responsive device.

Also, although pipe-foam assembly 13 is primarily intended to be permanently magnetized at some home base having optimum equipment and conditions for so doing, it is also to be understood that it may also be permanetly magnetized originally in the field, if the proper equipment that is, say, a suitable coil and direct current generator for supplying direct current electricity thereto is available thereat. Thus, it may be magnetized either at home base, aboard ship, or at some remote field location, whichever would facilitate the portability and use thereof, and whichever would provide safety and prevent destruction or adversely affect other apparatus or operations existing or going on in proximity therewith.

Moreover, it should readily be seen that the remagnetizing of pipe 13 is facilitated in the field of operations, in the event the demagnetization thereof should occur to some extent due to the occurrence of such deleterious things as mechanical or explosive shocks having been applied thereto. The latter, of course, appears to be one of the major distinct advantages over all of the known prior art.

From the foregoing, it may readily be seen that the subject invention constitutes an exceedingly simple but highly portable (and, thus, highly effective) means for detonating mines marine or otherwise and is especially useful for sweeping marine mines that have been deployed in shallow waters, where it has been proven to be very difficult and ordinarily unsafe to tactically maneuver the unweilding minesweeping apparatus of the prior art and its associated flotation equipment. Consequently, it is a vast improvement over any known prior art for such purpose.

As best seen in FIG. 4, in the event an exceedingly long magnetic field is required, or in the event a series of successive space-related magnetic fields is required for any given minesweeping or other operational circumstance, any desired number of magnetic AMCM pipes may be towed in properly spaced tandem configurations for such purposes. Of course, in such case as in the above described cases any or all of said AMCM pipes may have streamline configurations with or without stabilizer fins, and the propulsion means therefor may be a helicopter or other aircraft, a space vehicle, a land vehicle, a submarine vehicle, or any other suitable vehicle, as long as it provides sufficient motive power for whatever environmental medium it is operating in.

In the event the invention is utilized for magnetically influencing devices, apparatus, or equipment, including and excluding mines, in an environmental medium other than water, it would probably be necessary, or at least desirable, to select a tractor vehicle, a pipe assembly configuration, and, if needed, a trailing stabilizer (or combination thereof) that would be appropriate for such environment. Hence, in view of the teachings presented herewith, the making of the proper design selections of said elements would be well within the purview of one skilled in the art and, therfore, he would be able to do so without violating the spirit or scope of the invention.

Obviously, other embodiments and modifications of the subject invention will readily come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing description and the drawing. It is, therefore, to be understood that this invention is not to be limited thereto and that said modifications and embodiments are intended to be included within the scope of the appended claims.

What is claimed is:

l. A system for influencing magnetically responsive apparatus deployed within a predetermined environmental medium, comprising in combination:

a metallic pipe having a substantially circular cross sectional configuration and a predetermined bore along the length thereof, said metallic pipe being permanently magnetized in such manner as to effect a north magnetic pole at one end thereof and a south magnetic pole at the other end thereof, with a permanent magnetic field having a predetermined flux density therebetween that is effectively radiated around and from the entire-outer surface of said metallic pipe into said predetermined environmental medium;

foam means disposed within the bore of said metallic pipe, said foam means containing a plurality of closed compartments, each of which encapsulates a gaseous medium therein in such manner as to effect a predetermined density therefor, so as to, in turn, provide a predetermined buoyancy characteristic for said metallic pipe with respect to the aforesaid environmental medium;

an attachment means connected to one end of said metallic pipe; and

means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof.

2. The system of claim 1, wherein said magnetically responsive apparatus comprises magnetically responsive mines.

3. The system of claim 1, wherein said magnetically responsive apparatus comprises magnetically responsive marine mines, and wherein said predetermined environmental medium is water.

4. The system of claim 1, wherein said metallic pipe is a steel pipe.

5. The system of claim 1, wherein the gaseous medium encapsulated by the plurality of closed compartments of the aforesaid foam means comprises air.

6. The system of claim 1, wherein said attachment means connected to one end of said metallic pipe is a tow eye.

7. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises a tractor vehicle.

8. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises:

a helicopter; and

a tow cable connected between said helicopter and the aforesaid attachment means.

9. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises:

a boat; and

a tow cable connected between said boat and the aforesaid attachment means.

10. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises:

a submarine vehicle; and

a tow cable connected between said submarine vehicle and the aforesaid attachment means.

11. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises:

an aircraft; and

a tow cable connected between said aircraft and the aforesaid attachment means.

12. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises a land vehicle.

13. The invention of claim 1, further characterized by another attachment means connected to the other end of said metallic pipe.

14. The invention of claim 13, further characterized by a drag means effectively connected to said another attachment means connected to the other end of said metallic pipe for effecting the attitude stabilization thereof.

15. The invention of claim 14, wherein the drag means effectively connected to said other attachment means connected to the other end of said metallic pipe for effecting the stabilization thereof comprises a chain having a predetermined buoyancy characteristic relative to said predetermined environmental medium.

16. The system of claim 1, wherein said metallic pipe comprises a streamlined exterior configuration having a plurality of fins thereon for stabilization thereof.

17. The system of claim 1, wherein said foam means comprises polyurethane foam.

18. The system of claim 17, wherein said polyurethane foam means is NH COC H 19. A permanent magnet, comprising in combinatron:

a pipe, having a substantially circular cross-sectional configuration and a bore of predetermined length and inside diameter, that is permanently magnetized in such manner as to effect a north magnetic pole at one end thereof, a south magnetic pole at the other end thereof, and a permanent magnetic field having a predetermined flux density therebetween that is effectively radiated around and from the entire outer surface of said metallic pipe; and

a polyurethane foam, containing a plurality of closed compartments which respectively encapsulate a like plurality of air bubbles in such a manner as to provide such substantially uniform density therefor as will, in turn, provide a predetermined buoyancy therefor relative to a given environmental medium, disposed within the bore of said pipe.

20. The device of claim 19, wherein said pipe is a steel pipe having a substantially streamlined external configuration, and wherein said polyurethane foam is NH COC H 21. A method of effecting the destruction of a magnetically responsive marine mine that is located within an aqueous medium, comprising in combination the steps of:

selecting a pipe made of material capable of taking and retaining a permanent magnetization, having a suitable length, and containing a bore of predetermined diameter through the length thereof;

filling the bore of said pipe with a material, the density of which will cause the resulting pipe-material combination thereof to float at a given depth in water;

permanently magnetizing said pipe in such manner as to effect a north magnetic pole at one end thereof, a south magnetic pole at the other end thereof, and a permanent magnetic field having a predetermined flux density therebetween;

moving said permanently magnetized, float material filled pipe through said aqueous medium in such manner that the permanent magnetic field thereof comes within such proximity of said magnetically responsive marine mine to effect the detonation thereof. 

1. A system for influencing magnetically responsive apparatus deployed within a predetermined environmental medium, comprising in combination: a metallic pipe having a substantially circular cross-sectional configuration and a predetermined bore along the length thereof, said metallic pipe being permanently magnetized in such manner as to effect a north magnetic pole at one end thereof and a south magnetic pole at the other end thereof, with a permanent magnetic field having a predetermined flux density therebetween that is effectively radiated around and from the entire outer surface of said metallic pipe into said predetermined environmental medium; foam means disposed within the bore of said metallic pipe, said foam means containing a plurality of closed compartments, each of which encapsulates a gaseous medium therein in such manner as to effect a predetermined density therefor, so as to, in turn, provide a predetermined buoyancy characteristic for said metallic pipe with respect to the aforesaid environmental medium; an attachment means connected to one end of said metallic pipe; and means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof.
 2. The system of claim 1, wherein said magnetically responsive apparatus comprises magnetically responsive mines.
 3. The system of claim 1, wherein said magnetically responsive apparatus comprises magnetically responsive marine mines, and wherein said predetermined environmental medium is water.
 4. The system of claim 1, wherein said metallic pipe is a steel pipe.
 5. The system of claim 1, wherein the gaseous medium encapsulated by the plurality of closed compartments of the aforesaid foam means comprises air.
 6. The system of claim 1, wherein said attachment means connected to one end of said metallic pipe is a tow eye.
 7. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises a tractor vehicle.
 8. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises: a helicopter; and a tow cable connected between said helicopter and the aforesaid attachment means.
 9. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises: a boat; and a tow cable connected between said boat and the aforesaid attachment means.
 10. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises: a submarine vehicle; and a tow cable connected between said submarine vehicle and the aforesaid attachment means.
 11. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises: an aircraft; and a tow cable connected between said aircraft and the aforesaid attachment means.
 12. The system of claim 1, wherein said means effectively connected to said attachment means for effecting the movement of said metallic pipe through said predetermined environmental medium in proximity with the magnetically responsive apparatus to be influenced, so that said apparatus will be influenced by the permanent magnetic field thereof comprises a land vehicle.
 13. The invention of claim 1, further characterized by another attachment means connected to the other end of said metallic pipe.
 14. The invention of claim 13, further characterized by a drag means effectively connected to said another attachment means connected to the other end of said metallic pipe for effecting the attitude stabilization thereof.
 15. The invention of claim 14, wherein the drag means effectively connected to said other attachment means connected to the other end of said metallic pipe for effecting the stabilization thereof comprises a chain having a predetermined buoyancy characteristic relative to said predetermined environmental medium.
 16. The system of claim 1, wherein said metallic pipe comprises a streamlined exterior configuration having a plurality of fins thereon for stabilization thereof.
 17. The system of claim 1, wherein said foam means comprises polyurethane foam.
 18. The system of claim 17, wherein said polyurethane foam means is NH2 COC2 H5.
 19. A permanent magnet, comprising in combination: a pipe, having a substantially circular cross-sectional configuration and a bore of predetermined length and inside diameter, that is permanently magnetized in such manner as to effect a north magnetic pole at one end thereof, a south magnetic pole at the other end thereof, and a permanent magnetic field having a predetermined flux density therebetween that is effectively radiated around and from the entire outer surface of said metallic pipe; and a polyurethane foam, containing a plurality of closed compartments which respectively encapsulate a like plurality of air bubbles in such a manner as to provide such substantially uniform density therefor as will, in turn, provide a predetermineD buoyancy therefor relative to a given environmental medium, disposed within the bore of said pipe.
 20. The device of claim 19, wherein said pipe is a steel pipe having a substantially streamlined external configuration, and wherein said polyurethane foam is NH2 COC H5.
 21. A method of effecting the destruction of a magnetically responsive marine mine that is located within an aqueous medium, comprising in combination the steps of: selecting a pipe made of material capable of taking and retaining a permanent magnetization, having a suitable length, and containing a bore of predetermined diameter through the length thereof; filling the bore of said pipe with a material, the density of which will cause the resulting pipe-material combination thereof to float at a given depth in water; permanently magnetizing said pipe in such manner as to effect a north magnetic pole at one end thereof, a south magnetic pole at the other end thereof, and a permanent magnetic field having a predetermined flux density therebetween; moving said permanently magnetized, float material filled pipe through said aqueous medium in such manner that the permanent magnetic field thereof comes within such proximity of said magnetically responsive marine mine to effect the detonation thereof. 